Tyre for vehicle wheels and elastomeric composition

ABSTRACT

A crosslinkable elastomeric composition includes at least one diene elastomeric polymer and at least one organic quaternary ammonium salt. The at least one diene elastomeric polymer may have a glass transition temperature (T g ) below 20° C. The at least one organic quaternary ammonium salt may be present in an amount from 0.1 phr to 10 phr. The elastomeric composition may include at least one primary accelerator selected from thiazoles, sulphenamides, and/or xanthogenates. The elastomeric composition may be substantially free of additional secondary accelerators. The elastomeric composition may include at least one reinforcing filler, such as carbon black and/or silica. A tyre for a vehicle wheel includes at least one structural element including the elastomeric composition. The tyre may include a carcass structure, a belt structure, a tread band, and a pair of sidewalls. The at least one structural element including the elastomeric composition may be the tread band.

The present invention relates to a tyre for vehicle wheels, to a treadband and to a crosslinkable elastomeric composition.

More particularly, the present invention relates to a tyre for vehiclewheels comprising at least one structural element including anelastomeric composition comprising at least one organic quaternaryammonium salt.

The present invention moreover relates to a tread band including acrosslinkable elastomeric composition comprising at least one organicquaternary ammonium salt, and also to an elastomeric compositioncomprising at least one organic quaternary ammonium salt.

In the rubber industry, in particular in the manufacture of tyres forvehicle wheels, the use is known of elastomeric compositions whereinreinforcing fillers have been incorporated in the elastomeric polymerscommonly used, in order to improve the characteristics of the finalcrosslinked manufactured product, in particular mechanical propertiesand abrasion resistance. Thanks to its high reinforcing efficiency,carbon black is the most widely employed reinforcing filler. However,carbon black imparts to the crosslinked product marked hystereticcharacteristics, i.e. an increase of heat dissipated in dynamicconditions which, as is known, causes, in particular in the case of atyre, an increase in the rolling resistance of the tyre itself. Thisleads to an increase of the fuel consumption of the vehicles and henceof both locomotion costs and air pollution. It is possible to try toreduce the adverse effects by employing smaller amounts of carbon blackand/or a carbon black having a smaller surface area. This inevitablyleads to a reduction of the reinforcing action, with a worsening of themechanical properties and of the abrasion resistance of the finalcrosslinked manufactured product.

In order to reduce the hysteretic characteristics of the finalcrosslinked manufactured product it is known to use the so-called“white” reinforcing fillers such as, for example, gypsum, talc, kaolin,bentonite, titanium oxide, silicates of various types and in particularsilica, which may replace carbon black either entirely or partly. Inthis regard, see for example, European Patent EP 501,227.

The use of silica-based reinforcing fillers involves several drawbacks,substantially related to the poor affinity of the same with respects tothe elastomeric polymers commonly used in the tyre manufacture. Inparticular, to obtain a good dispersion degree of silica within theelastomeric polymers it is necessary to submit the elastomericcompositions to an extensive thermal-mechanical mixing action. Toincrease the affinity between silica and the elastomeric polymers, it isnecessary to employ suitable coupling agents such as, for example,sulfur-containing organosilane products. However, the need of using suchcoupling agents sets a limit to the maximum temperature that may bereached during mixing and thermal-mechanical processing operations, inorder to avoid an irreversible thermal degradation of the couplingagent.

Moreover, the use of silica-based reinforcing fillers in relativelylarge amounts causes an undesirable slowdown of the vulcanization rateof the elastomeric compositions. Usually, in order to increase saidvulcanization rate, it is known to add to the elastomeric compositions,besides the primary accelerators such as, for example, thiourea,sulfenamides, thiazoles, xanthogenates, secondary accelerators such as,for example, dithiocarbamates, thiouree, thiurams, Schiff's bases orother amino accelerators, guanidines, in particular diphenylguanidine(DPG). However, the presence of said secondary accelerators may, in somecases, entail considerable problems in terms of harmfulness/toxicityboth during production and during use. Moreover, diphenyl guanidine maycause, during the vulcanization step which is generally carried out attemperatures above 110° C., formation of aniline or aniline derivativeswhich are noxious by-products.

Moreover, the use of a primary accelerator combined with a secondaryaccelerator may cause a premature crosslinking of the elastomericcomposition at the temperatures commonly used during processing, so thatthe elastomeric composition may partially crosslink before the moldingand vulcanization step (“scorching”).

Attempts have been made in the prior art directed to increase thevulcanization rate of elastomeric compositions without causing scorchingphenomena.

For example, U.S. Pat. No. 4,861,842 discloses a vulcanizable rubbercomposition comprising a rubber and a vulcanization system comprising:from about 0.50 phr to about 2.0 phr of a sulfenamide accelerator, fromabout 0.10 phr to about 1.0 phr of a guanidine accelerator, from about0.10 phr to about 1. 0 phr of a thiuram accelerator, from about 0. 05phr to about 1.0 phr of mercapto benzothiazyl disulfide, from about 0.75phr to about 3.0 phr of a sulfur vulcanizing agent, from about 0.05 phrto about 0.50 phr of N-cyclohexylthio-phthalimide, from about 1. 0 phrto about 5.0 phr of a zinc compound, and from about 0.05 phr to about1.0 phr of an activator having the following formula:

wherein R¹, R² and R³ are independently alkyl radicals having from 8 to10 carbon atoms and M is selected from the group consiting of Cl, Br,CH₃SO₄ and HSO₄. Said vulcanizable rubber composition would show a veryfast vulcanization rate without prematurely crosslinking duringinjection molding.

U.S. Pat. No. 5,187,239 discloses a method for increasing thevulcanization rate of a rubber composition comprising adding to a sulfurvulcanizable rubber a methyl trialkyl ammonium salt having the followingformula:

wherein R¹, R² and R³ are independently alkyl radicals having from 8 to10 carbon atoms and M is selected from the group consiting of Cl, Br,CH₃SO₄ and HSO₄. In one embodiment, a single accelerator system may beused, i.e. primary accelerators such as, for example, a sulfenamide. Inanother embodiment, combination of two or more accelerators may be usedwhich may consist of a primary accelerator and a secondary acceleratorsuch as, for example, a guanidine, a dithiocarbamate or a thiuramcompound. The addition of a methyl trialkyl ammonium salt of the formuladisclosed above would significantly increase the vulcanization rate ofthe rubber.

U.S. Pat. No. 6,025,428 discloses sulfur-vulcanizable rubbercompositions having a silica filler incorporated with optimization ofthe silica associated properties relating to wear, wet traction androlling resistance. The silica associated properties are promoted bydispersing and coupling agents and, more particularly, the silicadispersion is improved through the use of a dispersing agent or aidcomprising a quaternary ammonium compound and the timely additionthereof during the rubber mixing or blending process so as to notunnecessarily inhibit the coupling agent enhancement. The dispersingagents are quaternary ammonium compounds having the following formula:

wherein R¹, R², R³ and R⁴, which may be the same or different, arealkyl, aryl and polyoxyethylene; and X is halogen. The delay incure/vulcanization of rubber observed with the use of silica would beenreduced by using the dispersing agents above disclosed. A furtheradvantage is that a secondary accelerator such as diphenyl guanidine(DPG) should not be necessary anymore.

In the Applicant's view, crosslinkable elastomeric compositions whereinthe amount of secondary accelerators is reduced, or even eliminated,should satisfy a number of requirements in order to make themadvantageously useful in the production of crosslinked manufacturedproducts, and in particular of tyres. As a matter of fact, the reductionor elimination of secondary accelerators should not compromise thefundamental properties of the crosslinked manufactured products, such asmechanical properties (both static and dynamic), as well as abrasionresistance. Moreover, said reduction or elimination should not decreasethe vulcanization rate, so as to maintain it at an acceptable level fromthe point of view of industrial production.

The Applicant has now found that it is possible to obtain crosslinkableelastomeric compositions capable of being used advantageously in theproduction of crosslinked manufactured products, in particular in theproduction of tyre, using at least one organic quaternary ammonium salthaving at least one group containing a non-ionic nitrogen atom as asecondary accelerator. The addition of said organic quaternary ammoniumsalt provides, even in the substantial absence of additional secondaryaccelerators, a crosslinked manufactured product that has goodmechanical properties (both static and dynamic), while maintainingacceptable vulcanization rate. Applicant has also found that by using atleast one organic quaternary ammonium salt as defined above having asanion group a carboxylate anion, it is possible to avoid also the use ofstearic acid which, as known in the art, is usually used as avulcanization activator.

According to a first aspect, the present invention thus relates to atyre for vehicle wheels, comprising at least one structural elementincluding an elastomeric composition comprising:

-   -   (a) at least one diene elastomeric polymer;    -   (b) at least one organic quaternary ammonium salt having the        following general formula (I):    -   wherein:        -   R represents a linear or branched C₁-C₂₂ alkylene group; a            linear or branched C₂-C₂₂ alkenylene group; a C₆-C₁₈ arylene            group; a C₁-C₂₀ alkylarylene or alkylenearylene group; said            groups optionally containing at least one heteroatom            selected from oxygen, nitrogen or sulfur;        -   R₁ and R₂, which may be identical or different, represent a            linear or branched C₁-C₂₂ alkyl group; a linear or branched            C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group; a C₇-C₂₀            arylalkyl or alkylaryl group; said groups optionally            containing at least one heteroatom selected from oxygen,            nitrogen or sulfur; or, R₁ and R₂, considered jointly with            the nitrogen atom to which they are linked, represent a            C₅-C₁₈ heterocyclic ring optionally containing a second            heteroatom selected from oxygen, nitrogen or sulfur; or, R₁            and R₅ and/or R₂ and R₃, considered jointly with the            nitrogen atoms to which they are linked, represent a C₅-C₁₈            heterocyclic ring;        -   R₃, R₄ and R₅, which may be identical or different,            represent a linear or branched C₁-C₂₂ alkyl group; a linear            or branched C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group; a            C₇-C₂₀ arylalklyl or alkylaryl group; a group having the            following formula:        -   wherein R, R₁ and R₂, have the same meanings as disclosed            above; or two from R₃, R₄ and R₅, considered jointly with            the nitrogen atom to which they are linked, represent a            C₅-C₁₈ heterocyclic ring optionally containing a second            heteroatom selected from oxygen, nitrogen or sulfur;        -   X^(n−) represents an inorganic or organic anion group;        -   n represents 1, 2 or 3.

According to one preferred embodiment, the present invention relates toa tyre for vehicle wheels, comprising:

-   -   a carcass structure with at least one carcass ply shaped in a        substantially toroidal configuration, the opposite lateral edges        of which are associated with respective right-hand and left-hand        bead wires, each bead wire being enclosed in a respective bead;    -   a belt structure comprising at least one belt strip applied in a        circumferentially external position relative to said carcass        structure;    -   a tread band superimposed circumferentially on said belt        structure;    -   a pair of side walls applied laterally on opposite sides        relative to said carcass structure;        wherein said structural element which includes said elastomeric        composition is the tread band.

According to a further aspect, the present invention relates to a tyretread band including a crosslinkable elastomeric composition comprising:

-   -   (a) at least one diene elastomeric polymer;    -   (b) at least one organic quaternary ammonium salt having the        following general formula (I):    -   wherein:        -   R represents a linear or branched C₁-C₂₂ alkylene group; a            linear or branched C₂-C₂₂ alkenylene group; a C₆-C₁ arylene            group; a C₇-C₂₀ alkylarylene or alkylenearylene group; said            groups optionally containing at least one heteroatom            selected from oxygen, nitrogen or sulfur;        -   R₁ and R₂, which may be identical or different, represent a            linear or branched C₁-C₂₂ alkyl group; a linear or branched            C₂-C₂₂ alkenyl group; a C₆-C₁₆ aryl group; a C₇-C₂₀            arylalkyl or alkylaryl group; said groups optionally            containing at least one heteroatom selected from oxygen,            nitrogen or sulfur; or, R₁ and R₂, considered jointly with            the nitrogen atom to which they are linked, represent a            C₅-C₁₈ heterocyclic ring optionally containing a second            heteroatom selected from oxygen, nitrogen or sulfur; or, R₁            and R₅ and/or R₂ and R₃, considered jointly with the            nitrogen atoms to which they are linked, represent a C₅-C₁₈            heterocyclic ring;        -   R₃, R₄ and R₅, which may be identical or different,            represent a linear or branched C₁-C₂₂ alkyl group; a linear            or branched C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group; a            C₇-C₂₀ arylalklyl or alkylaryl group; a group having the            following formula:        -   wherein R, R₁ and R₂, have the same meanings as disclosed            above; or two from R₃, R₄ and R₅, considered jointly with            the nitrogen atom to which they are linked, represent a            C₅-C₁₈ heterocyclic ring optionally containing a second            heteroatom selected from oxygen, nitrogen or sulfur;        -   X^(n−) represents an inorganic or organic anion group;        -   n represents 1, 2 or 3.

According to a further aspect, the present invention relates to acrosslinkable elastomeric composition comprising:

-   -   (a) at least one diene elastomeric polymer;    -   (b) at least one organic quaternary ammonium salt having the        following general formula (I):    -   wherein:        -   R represents a linear or branched C₁-C₂₂ alkylene group; a            linear or branched C₂-C₂₂ alkenylene group; a C₆-C₁₈ arylene            group; a C₇-C₂₀ alkylarylene or alkylenearylene group; said            groups optionally containing at least one heteroatom            selected from oxygen, nitrogen or sulfur;        -   R₁ and R₂, which may be identical or different, represent a            linear or branched C₃-C₂₂ alkyl group; a linear or branched            C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group; a C₇-C₂₀            arylalkyl or alkylaryl group; said groups optionally            containing at least one heteroatom selected from oxygen,            nitrogen or sulfur; or, R₁ and R₂, considered jointly with            the nitrogen atom to which they are linked, represent a            C₅-C₁₈ heterocyclic ring optionally containing a second            heteroatom selected from oxygen, nitrogen or sulfur; or, R₁            and R₅ and/or R₂ and R₃, considered jointly with the            nitrogen atoms to which they are linked, represent a C₅-C₁₈            heterocyclic ring;        -   R₃, R₄ and R₅, which may be identical or different,            represent a linear or branched C₁-C₂₂ alkyl group; a linear            or branched C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group; a            C₇-C₂₀ arylalklyl or alkylaryl group; a group having the            following formula:        -   wherein R, R₁ and R₂, have the same meanings as disclosed            above; or two from R₃, R₄ and R₅, considered jointly with            the nitrogen atom to which they are linked, represent a            C₅-C₁₈ heterocyclic ring optionally containing a second            heteroatom selected from oxygen, nitrogen or sulfur;        -   X^(n−) represents an inorganic or organic anion group;        -   n represents 1, 2 or 3.

According to a further aspect, the present invention relates to acrosslinked elastomeric manufactured product obtained by crosslinkingthe abovementioned elastomeric composition.

According to one preferred embodiment, said elastomeric composition issubstantially free of additional secondary accelerators [i.e. differentfrom the organic quaternary ammonium salt having general formula (I)],such as, for example, guanidines (e.g. diphenyl guanidine), thiurames,dithiocarbamates, Schiff's bases or other amino accelerators, thiouree.

According to a further preferred embodiment, said elastomericcomposition is substantially free of diphenyl guanidine (DPG).

According to a further preferred embodiment, said elastomericcomposition may further comprise at least one primary accelerator (c).

For the purposes of the present description and of the claims whichfollows:

-   -   the term “primary accelerator” refers to a compound which        increases the vulcanization rate of an elastomeric composition        so as to obtain an appreciable degree of crosslinking in an        industrially acceptable time; as    -   the term “secondary accelerator” refers to a compound which        appreciably increases the vulcanization rate of an elastomeric        composition in the presence of a “primary accelerator” by        enhancing the effectiveness of the latter.

According to one preferred embodiment, X^(n−) may be selected, forexample, from: halide ions such as, for example, iodine, bromine,fluorine, or chlorine ions; ipoiodite ion; ipobromite ion; fluorite ion;chlorite ion; iodite ion; bromite ion; fluorine ion; chlorite ion;iodate ion; bromate ion; fluorate ion; chlorate ion; periodate ion;perbromate ion; perfluorate ion; perchlorate ion; nitrate ion; nitriteion; sulfate ion; sulfite ion; phosphate ion; phosphite ion; hydroxideion; or an anion represented by the following formulae (II) to (V):R₆COO⁻   (II)wherein R₆ represents a linear or branched C₁-C₁₈ alkyl group; a linearor branched C₂-C₁₈ alkenyl group; a C₆-C₁₈ aryl group; a C₇-C₂₀arylalklyl or alkylaryl group; said groups optionally containing atleast one of the following groups: hydroxyl group, carbonyl group, ethergroup, thioether group, ester group;⁻OCO—(R₇)_(m)—COO⁻   (III)wherein m represents 0 or 1; R₇ represents a linear or branched C₁-C₁₈alkylene group; a linear, branched or cyclic C₂-C₁₈ alkenylene group; aC₆-C₁₈ arylene group; a C₇-C₂₀ arylalklylene or alkylarylene group; saidgroups optionally containing at least one of the following groups:hydroxyl group, carbonyl group, ether group, thioether group, estergroup;,R₈SO_(p) ⁻   (IV)wherein p represent 3 or 4; R₈ represents a linear or branched C₁-C₁₈alkyl group; a linear or branched C₂-C₁₈ alkenyl group; a C₆-C₁₈ arylgroup; a C₇-C₂₀ arylalklyl or alkylaryl group; said groups optionallycontaining at least one of the following groups: hydroxyl group,carbonyl group, ether group, thioether group, ester group;

wherein p represents 3 or 4; R₉ and R₁₀, which may be identical ordifferent, represent a hydrogen atom; a linear or branched C₁-C₁₈ alkylgroup; a linear or branched C₂-C₁₈ alkenyl group; a C₆-C₁₈ aryl group; aC₇-C₂₀ arylalklyl or alkylaryl group; said groups optionally containingat least one of the following groups: hydroxyl group, carbonyl group,ether group, thioether group, ester group.

Examples of R and R₇ groups are: methylene, ethylene, propylene,butylene, 2,2-dimethyl-1,3-propylene, hexylene,2-methyl-3-ethyl-1,4-butylene, octylene, vinylene, butenylene,isobutenylene, pentenylene, hexenylene, phenylene, naphtylene,diphenylene, benzenylene, phenylmethylene, phenylethylene,naphtylmethylene, naphtylethylene, methylphenylene, ethylphenylene,methylnaphthylene, ethylnaphthylene.

Examples of R₁, R₂, R₃, R₄, R₅, R₆, R₈, R₉ and R₁₀ groups are: methyl,ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, octyl, allyl,methallyl, 2-butenyl, propenyl, hexenyl, octenyl, benzyl, phenyl,naphthyl, methylbenzyl, ethylbenzyl, diphenyl, methylphenyl,ethylphenyl, methylnaphthyl, ethylnaphthyl.

Examples of R₁ and R₂ considered jointly with the nitrogen atom to whichthey are linked are: morpholine, pyrrolidine, piperidine,N-methyl-piperidine, piperazine, thiomorpholine, thiazolidine,benzothiazolidine, imidazole.

Examples of R₁ and R₅ and/or R₂ and R₃ considered jointly with thenitrogen atom to which they are linked are: piperazine,1,8-diazabicyclo[2.2.2]octane.

Examples of heterocyclic rings in the case wherein two from R₃, R₄ andR₅, considered jointly with the nitrogen atom to which they are linked,represent a C₅-C₁₈ heterocyclic ring are: pyrrolidinium, piperidinium,piperazinium, imidazolium.

According to one preferred embodiment, said organic quaternary ammoniumsalt (b) is present in the elastomeric composition in an amount of from0.1 phr to 10 phr, preferably from 0.5 phr to 5 phr.

For the purposes of the present description and of the claims whichfollows, the term “phr” means the parts by weight of a given componentof the elastomeric composition per 100 parts by weight of theelastomeric polymer.

The quaternary ammonium salt (b) may be added to the elastomericcomposition according to the present invention as such or supported on acarrier such as, for example, silica, alumina, carbon black; ordispersed in a polymeric carrier so as to obtain a product in subdividedform (see, for example, the International Patent Application WO02/083783 in the name of the same Applicant). Alternatively, thequaternary ammonium salt (b) may be used as a solution, e.g. dissolvedin a hydroalcoholic solvent such as, for example, water/ethanol,water/isopropanol.

The quaternary ammonium salt (b) may be prepared according to thefollowing processes.

For example, the quaternary ammonium salt (b) may be prepared by aprocess comprising the reaction of an-amine having the following formula(VI):

wherein R, R₁, R₂, R₃ and R₄ have the same meanings as disclosed above,with a halogen compound having the following formula (VII):R₅—Y   (VII)wherein R₅ has the same meanings as disclosed above and Y represents ahalogen atom selected from iodine, bromine, fluorine, or chlorine. Thereaction may be carried out both at room temperature or at a refluxtemperature in the presence of an organic solvent selected, for example,from ethers such as, for example, diethyl ether, dipropyl ether,diisopropyl ether, dibutyl ether, t-butyl methyl ether, diisoamyl ether,tetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxyethane, or mixturesthereof; ketones such as, for example, acetone, methyl ethyl ketone,methyl isobutyl ketone, methyl amyl ketone, cyclohexanone; acetonitrile;toluene; or mixture thereof.

Alternatively, the quaternary ammonium salt (b) may be obtained asdisclosed, for example, in Bull. Chem. Soc. Jpn. (1986); Vol. 59, pg.2699-2705.

The quaternary ammonium salt (b) obtained as disclosed above, may befurther reacted with a base such as, for example, sodium hydroxide,potassium hydroxide, in stechiometric amount, at room temperature, inthe presence of an organic solvent selected, for example, from alcoholssuch as, for example, methanol, ethanol, n-propanol, acetone, ormixtures therof, obtaining a solid product. The obtained solid productis then treated with an alcoholic solution (for example, ethanolsolution) of a compound having the following formula (VIII):R₆COOH   (VIII)wherein R₆ has the same meanings as disclosed above, in a stechiometricamount, at reflux temperature.

According to one preferred embodiment, the diene elastomeric polymer (a)which may be used in the present invention may be selected from thosecommonly used in sulphur-crosslinkable elastomeric compositions, thatare particularly suitable for producing tyres, that is to say fromelastomeric polymers or copolymers with an unsaturated chain having aglass transition temperature (T_(g)) generally below 20° C., preferablyin the range of from 0° C. to −90° C. These polymers or copolymers maybe of natural origin or may be obtained by solution polymerization,emulsion polymerization or gas-phase polymerization of one or moreconjugated diolefins, optionally blended with at least one comonomerselected from monovinylarenes and/or polar comonomers in an amount ofnot more than 60% by weight.

The conjugated diolefins generally contain from 4 to 12, preferably from4 to 8 carbon atoms, and may be selected, for example, from the groupcomprising: 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene,1,3-pentadiene, 1,3-hexadiene, 3-butyl-1,3-octadiene,2-phenyl-1,3-butadiene, or mixtures thereof. 1,3-butadiene and isopreneare particularly preferred.

Monovinylarenes which may optionally be used as comonomers generallycontain from 8 to 20, preferably from 8 to 12 carbon atoms, and may beselected, for example, from: styrene; 1-vinylnaphthalene;2-vinylnaphthalene; various alkyl, cycloalkyl, aryl, alkylaryl orarylalkyl derivatives of styrene such as, for example, α-methylstyrene,3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene,2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4-phenylbutyl)styrene, ormixtures thereof. Styrene is particularly preferred.

Polar comonomers which may optionally be used may be selected, forexample, from: vinylpyridine, vinylquinoline, acrylic acid andalkylacrylic acid esters, nitriles, or mixtures thereof, such as, forexample, methyl acrylate, ethyl acrylate, methyl methacrylate, ethylmethacrylate, acrylonitrile, or mixtures thereof.

Preferably, the diene elastomeric polymer (a) which may be used in thepresent invention may be selected, for example, from:cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber),3,4-polyisoprene, polybutadiene (in particular polybutadiene with a high1,4-cis content), optionally halogenated isoprene/isobutene copolymers,1,3-butadiene/acrylonitrile copolymers, styrene/1,3-butadienecopolymers, styrene/isoprene/1,3-butadiene copolymers,styrene/1,3-butadiene/acrylonitrile copolymers, or mixtures thereof.

The elastomeric composition according to the present invention mayoptionally comprise at least one elastomeric polymer of one or moremonoolefins with an olefinic comonomer or derivatives thereof (a′). Themonoolefins may be selected from: ethylene and α-olefins generallycontaining from 3 to 12 carbon atoms, such as, for example, propylene,1-butene, 1-pentene, 1-hexene, 1-octene, or mixtures thereof. Thefollowing are preferred: copolymers between ethylene and an α-olefin,optionally with a diene; isobutene homopolymers or copolymers thereofwith small amounts of a diene, which are optionally at least partiallyhalogenated. The diene optionally present generally contains from 4 to20 carbon atoms and is preferably selected from: 1,3-butadiene,isoprene, 1,4-hexadiene, 1,4-cyclohexadiene, 5-ethylidene-2-norbornene,5-methylene-2-norbornene, vinylnorbornene, or mixtures thereof. Amongthese, the following are particularly preferred: ethylene/propylenecopolymers (EPR) or ethylene/propylene/diene copolymers (EPDM);polyisobutene; butyl rubbers; halobutyl rubbers, in particularchlorobutyl or bromobutyl rubbers; or mixtures thereof.

A diene elastomeric polymer (a) or an elastomeric polymer (a′)functionalized by reaction with suitable terminating agents or couplingagents may also be used. In particular, the diene elastomeric polymersobtained by anionic polymerization in the presence of an organometallicinitiator (in particular an organolithium initiator) may befunctionalized by reacting the residual organometallic groups derivedfrom the initiator with suitable terminating agents or coupling agentssuch as, for example, imines, carbodiimides, alkyltin halides,substituted benzophenones, alkoxysilanes or aryloxysilanes (see, forexample, European patent EP 451 604, or patents U.S. Pat. Nos. 4,742,124and 4,550,142).

The silica based reinforcing filler which may be used in the presentinvention may be selected from a pyrogenic silica or, preferably, aprecipitated silica, with a BET surface area (measured according to ISOstandard 5794/1) of from 50 m²/g to 500 m²/g, preferably from 70 m²/g to200 m²/g.

As disclosed above, the elastomeric composition according to the presentinvention, may further comprises at least one primary accelerator (c).

According to one preferred embodiment, the primary accelerator (c) maybe selected, for example, from:

-   -   thiazoles such as, for example, 2-mercaptobenzothiazole (MBT),        zinc salt of 2-mercaptobenzothiazole (ZMBT),        2-mercaptobenzothiazole disulphide (MBTS),        2,4-dinitrophenylmercaptobenzothiazole;    -   sulphenamides such as, for example,        N-cyclohexyl-2-benzothiazylsulphenamide (CBS),        N-oxydiethylene-2-benzothiazylsulphenamide (OBS),        N-t-butyl-2-benzothiazylsulphenamide (TBBS),        N,N-dicyclohexyl-2-benzothiazylsulphenamide (DCBS);    -   xanthogenates such as, for example, zinc isopropylxanthogenate        (ZIX), zinc butylxanthogenate (ZBX), sodium        isopropylxanthogenate (NaIX), dibutylxanthogenate disulphide        (DBX);        or mixtures thereof. Preferably sulphenamides are used, more        preferably N-cyclohexyl-2-benzothiazylsulphenamide (CBS) and        N-t-butyl-2-benzothiazylsulphenamide (TBBS), are used

According to one preferred embodiment, said primary accelerator (c) ispresent in the elastomeric composition in an amount of from 0.1 phr to10 phr, preferably from 0.5 phr to 5 phr.

At least one reinforcing filler may advantageously be added to theelastomeric composition according to the present invention, in an amountgenerally of between 0.1 phr and 120 phr, preferably between 20 phr and90 phr. The reinforcing filler may be chosen from those commonly usedfor crosslinked manufactured products, in particular for tyres, such as,for example, carbon black, silica, alumina, aluminosilicates, calciumcarbonate, kaolin, or mixtures thereof.

The types of carbon black which may be used according to the presentinvention may be chosen from those conventionally used in the productionof tyres, generally having a surface area of not less than 20 m²/g(determined by CTAB absorption as described in ISO standard 6810).

The silica which may be used according to the present invention maygenerally be a pyrogenic silica or, preferably, a precipitated silica,with a BET surface area (measured according to ISO standard 5794/1) ofbetween 50 M²/g and 500 m²/g, preferably between 70 m²/g and 200 m²/g.

When a reinforcing filler comprising silica is present, the elastomericcomposition may advantageously incorporate a coupling agent capable ofacting with the silica and of linking it to the elastomeric base duringthe vulcanization.

Coupling agents that are preferably used are those based on silane whichmay be identified, for example, by the following structural formula(IX):(R)₃Si—C_(n)H_(2n)—X   (IX)in which the groups R, which may be identical or different, are chosenfrom: alkyl, alkoxy or aryloxy groups or from halogen atoms, oncondition that at least one of the groups R is an alkoxy or aryloxygroup; n is an integer between 1 and 6 inclusive; X is a group chosenfrom: nitroso, mercapto, amino, epoxide, vinyl, imide, chloro,—(S)_(m)C_(n)H_(2n)—Si—(R)₃ in which m and n are integers between 1 and6 inclusive and the groups R are defined as above.

Among the coupling agents that are particularly preferred arebis(3-triethoxysilylpropyl) tetrasulphide andbis(3-triethoxysilylpropyl) disulphide. Said coupling agents may be usedas such or as a suitable mixture with an inert filler (for examplecarbon black) so as to facilitate their incorporation into theelastomeric composition.

The elastomeric composition according to the present invention may bevulcanized according to known techniques, in particular withsulphur-based vulcanizing systems commonly used for diene elastomericpolymers. To this end, in the elastomeric composition, after one or twosteps of thermomechanical processing, a sulphur-based vulcanizing agentis incorporated together with vulcanization accelerators. In this secondor third processing step, the temperature is generally kept below 120°C. and preferably below 100° C., so as to avoid any unwantedpre-crosslinking phenomena. The organic quaternary ammonium salt (b) maybe added to the elastomeric composition according to the presentinvention during any one of the above reported steps.

The vulcanizing agent most advantageously used is sulphur, or moleculescontaining sulphur (sulphur donors), with accelerators and activatorsknown to those skilled in the art.

Activators that are particularly effective are zinc compounds, and inparticular ZnO, ZnCO₃, zinc salts of saturated or unsaturated fattyacids containing from 8 to 18 carbon atoms, such as, for example, zincstearate, which are preferably formed in situ in the elastomericcomposition from ZnO and fatty acid such as, for example, stearic acid,and also BiO, PbO, Pb₃O₄, PbO₂, or mixtures thereof. As alreadydisclosed above, in the case of an organic quaternary ammonium salt (b)wherein the anion group is a carboxylate anion, the addition of stearicacid may be avoided.

The elastomeric composition according to the present invention mayfurther comprise other commonly used additives selected on the basis ofthe specific application for which the composition is intended. Forexample, the following may be added to said composition: antioxidants,anti-ageing agents, plasticizers, adhesives, anti-ozone agents,modifying resins, fibres (for example Kevlar® pulp), or mixturesthereof.

In particular, for the purpose of further improving the processability,a plasticizer generally selected from mineral oils, vegetable oils,synthetic oils, or mixtures thereof, such as, for example, aromatic oil,naphthenic oil, phthalates, soybean oil, or mixtures thereof, may beadded to the elastomeric composition according to the present invention.The amount of plasticizer generally ranges from 2 phr to 100 phr,preferably from 5 phr to 50 phr.

The elastomeric composition according to the present invention may beprepared by mixing together the diene elastomeric polymers with thereinforcing filler and with the other additives optionally presentaccording to techniques known in the art. The mixing may be carried out,for example, using an open mixer of open-mill type, or an internal mixerof the type with tangential rotors (Banbury) or with interlocking rotors(Intermix), or in continuous mixers of Ko-Kneader type (Buss) or ofco-rotating or counter-rotating twin-screw type.

The present invention will now be illustrated in further detail by meansof a number of illustrative embodiments, with reference to the attachedFIG. 1, which is a view in cross section of a portion of a tyre madeaccording to the invention.

“a” indicates an axial direction and “r” indicates a radial direction.For simplicity, FIG. 1 shows only a portion of the tyre, the remainingportion not represented being identical and symmetrically arranged withrespect to the radial direction “r”.

The tyre (100) comprises at least one carcass ply (101), the oppositelateral edges of which are associated with respective bead wires (102).The association between the carcass ply (101) and the bead wires (102)is achieved here by folding back the opposite lateral edges of thecarcass ply (101) around the bead wires (102) so as to form theso-called carcass back-folds (101 a) as shown in FIG. 1.

Alternatively, the conventional bead wires (102) can be replaced with apair of circumferentially inextensible annular inserts formed fromelongate components arranged in concentric coils (not represented inFIG. 1) (see, for example, European patent applications EP 928,680 andEP 928,702). In this case, the carcass ply (101) is not back-foldedaround said annular inserts, the coupling being provided by a secondcarcass ply (not represented in FIG. 1) applied externally over thefirst.

The carcass ply (101) generally consists of a plurality of reinforcingcords arranged parallel to each other and at least partially coated witha layer of elastomeric compound. These reinforcing cords are usuallymade of textile fibres, for example rayon, nylon or polyethyleneterephthalate, or of steel wires stranded together, coated with a metalalloy (for example copper/zinc, zinc/manganese, zinc/molybdenum/cobaltalloys and the like).

The carcass ply (101) is usually of radial type, i.e. it incorporatesreinforcing cords arranged in a substantially perpendicular directionrelative to a circumferential direction. Each bead wire (102) isenclosed in a bead (103), defined along an inner circumferential edge ofthe tyre (100), with which the tyre engages on a rim (not represented inFIG. 1) forming part of a vehicle wheel. The space defined by eachcarcass back-fold (101 a) contains a bead filler (104) wherein the beadwires (102) are embedded. An antiabrasive strip (105) is usually placedin an axially external position relative to the carcass back-fold (101a).

A belt structure (106) is applied along the circumference of the carcassply (101). In the particular embodiment in FIG. 1, the belt structure(106) comprises two belt strips (106 a, 106 b) which incorporate aplurality of reinforcing cords, typically metal cords, which areparallel to each other in each strip and intersecting with respect tothe adjacent strip, oriented so as to form a predetermined anglerelative to a circumferential direction. On the radially outermost beltstrip (106 b) may optionally be applied at least one zero-degreereinforcing layer (106 c), commonly known as a “0° belt”, whichgenerally incorporates a plurality of reinforcing cords, typicallytextile cords, arranged at an angle of a few degrees relative to acircumferential direction, and coated and welded together by means of anelastomeric material.

A side wall (108) is also applied externally onto the carcass ply (101)this side wall extending, in an axially external position, from the bead(103) to the end of the belt structure (106).

A tread band (109), whose lateral edges are connected to the side walls(108), is applied circumferentially in a position radially external tothe belt structure (106). Externally, the tread band (109) has a rollingsurface (109 a) designed to come into contact with the ground.Circumferential grooves which are connected by transverse notches (notrepresented in FIG. 1) so as to define a plurality of blocks of variousshapes and sizes distributed over the rolling surface (109 a) aregenerally made in this surface (109 a), which is represented forsimplicity in FIG. 1 as being smooth.

A strip made of elastomeric material (110), commonly known as a“mini-side wall”, may optionally be present in the connecting zonebetween the side walls (108) and the tread band (109), this mini-sidewall generally being obtained by co-extrusion with the tread band andallowing an improvement in the mechanical interaction between the treadband (109) and the side walls (108). Alternatively, the end portion ofthe side wall (108) directly covers the lateral edge of the tread band(109). A underlayer which forms, with the tread band (109), a structurecommonly known as a “cap and base” (not represented in FIG. 1) mayoptionally be placed between the belt structure (106) and the tread band(109).

A layer of elastomeric material (111) which serves as an “attachmentsheet”, i.e. a sheet capable of providing the connection between thetread band (109) and the belt structure (106), may be placed between thetread band (109) and the belt structure (106).

In the case of tubeless tyres, a rubber layer (112) generally known as a“liner”, which provides the necessary impermeability to the inflationair of the tyre, may also be provided in a radially internal positionrelative to the carcass ply (101).

The process for producing the tyre according to the present inventionmay be carried out according to techniques and using apparatus that areknown in the art, as described, for example, in patents EP 199 064, U.S.Pat. Nos. 4,872,822, 4,768,937, said process including at least one stepof manufacturing the green tyre and at least one step of vulcanizingthis tyre.

More particularly, the process for producing the tyre comprises thesteps of preparing, beforehand and separately from each other, a seriesof semi-finished products corresponding to the various parts of the tyre(carcass plies, belt structure, bead wires, fillers, side walls andtread band) which are then combined together using a suitablemanufacturing machine. Next, the subsequent vulcanization step welds theabovementioned semi-finished products together to give a monolithicblock, i.e. the finished tyre.

Naturally, the step of preparing the abovementioned semi-finishedproducts will be preceded by a step of preparing and moulding thevarious blends, of which said semi-finished products are made, accordingto conventional techniques.

The green tyre thus obtained is then passed to the subsequent steps ofmoulding and vulcanization. To this end, a vulcanization mould is usedwhich is designed to receive the tyre being processed inside a mouldingcavity having walls which are countermoulded to define the outer surfaceof the tyre when the vulcanization is complete.

Alternative processes for producing a tyre or parts of a tyre withoutusing semi-finished products are disclosed, for example, in theabovementioned patent applications EP 928,680 and EP 928,702.

The green tyre may be moulded by introducing a pressurized fluid intothe space defined by the inner surface of the tyre, so as to press theouter surface of the green tyre against the walls of the mouldingcavity. In one of the moulding methods widely practised, a vulcanizationchamber made of elastomeric material, filled with steam and/or anotherfluid under pressure, is inflated inside the tyre closed inside themoulding cavity. In this way, the green tyre is pushed against the innerwalls of the moulding cavity, thus obtaining the desired moulding.Alternatively, the moulding may be carried out without an inflatablevulcanization chamber, by providing inside the tyre a toroidal metalsupport shaped according to the configuration of the inner surface ofthe tyre to be obtained as decribed, for example, in patent EP 242,840.The difference in coefficient of thermal expansion between the toroidalmetal support and the crude elastomeric material is exploited to achievean adequate moulding pressure.

At this point, the step of vulcanizing the crude elastomeric materialpresent in the tyre is carried out. To this end, the outer wall of thevulcanization mould is placed in contact with a heating fluid (generallysteam) such that the outer wall reaches a maximum temperature generallyof between 100° C. and 230° C. Simultaneously, the inner surface of thetyre is heated to the vulcanization temperature using the samepressurized fluid used to press the tyre against the walls of themoulding cavity, heated to a maximum temperature of between 100° C. and250° C. The time required to obtain a satisfactory degree ofvulcanization throughout the mass of the elastomeric material may varyin general between 3 min and 90 min and depends mainly on the dimensionsof the tyre. When the vulcanization is complete, the tyre is removedfrom the vulcanization mould.

Although the present invention has been illustrated specifically inrelation to a tyre, other crosslinked elastomeric manufactured productsthat may be produced according to the invention may be, for example,conveyor belts, driving belts or flexible tubes.

The present invention will be further illustrated below by means of anumber of preparation examples, which are given for purely indicativepurposes and without any limitation of this invention.

EXAMPLE 1 Preparation of the Organic Quaternary Ammonium Salt

In a 1 1 reaction vessel were charged 0.15 mol of 1-bromo-decane, 0.18mol of 1,4-diaza-biciclo[2.2.2]octane (DABCO) and 400 ml of t-butylmethyl ether. The reaction mixture was then heated at reflux temperaturefor 21 hours.

The t-butyl methyl ether was then removed from the reaction productunder reduced pressure obtaining a solid product.

The solid product so obtained was then filtered, washed with t-butylmethyl ether and dried under reduced pressure to obtain 41.87 g (yield83.7%) of the desired product.

EXAMPLE 2 Preparation of the Organic Quaternary Ammonium Salt

In a 1 1 reaction vessel were charged 0.15 mol of 1-chloro-eptane, 0.18mol of 1,4-diazabiciclo[2.2.2]octane (DABCO) and 400 ml of acetone. Thereaction mixture was then heated at reflux temperature for 24 hours.

The acetone was then removed from the reaction product under reducedpressure obtaining an oil.

The obtained oil was washed with diethyl ether and then dried underreduced pressure to obtain a 29.2 g (yield 79%) of the desired product.

EXAMPLE 3 Preparation of the Organic Quaternary Ammonium Salt

In a 250 ml reaction vessel were charged 0.084 mol of the quaternaryammonium salt obtained as disclosed in Example 1, 0.084 mol of potassiumhydroxide and 90 ml of ethanol. The reaction mixture was then stirred,at room temperature, for 30 minutes. Then, the solution was cooled at 0°C. and was kept at this temperature for 30 minutes obtainig a solidproduct.

The obtained solid product was then filtered, washed with 10 ml of coldethanol and then treated with a solution of 0.084 ml of stearic acid in124 ml of ethanol.

The obtained solution was then heated at reflux temperature for 1 hour.A white solid product was precipitated at room temperature and removedby filtration. The filtered solution was concentrated at reducedpressure, at 50° C., to obtain a solid product which was then washedwith tetrahydrofuran and dried under reduced pressure to obtain 18.56 g(78%) of the desired product.

EXAMPLE 4-8 Preparation of the Elastomeric Compositions

The elastomeric compositions given in Table 1 were prepared as follows(the amounts of the various components are given in phr).

All the ingredients, except zinc oxide, sulphur, antioxidant, ammoniumsalt, and accelerator, were mixed together in an internal mixer (modelPomini PL 1.6) for about 5 min (1^(st) Step). When a temperature of145±5° C. was reached, the elastomeric composition was discharged. Thenzinc oxide and antioxidant were added and mixing was carried out in aninternal mixer (model Pomini PL 1.6) for about 5 min (₂nd Step). When atemperature of 125±5° C. was reached, the elastomeric composition wasdischarged. Then sulphur, ammonium salt and accelerator were added andmixing was carried out in an open roll mixer (3^(rd) Step). TABLE 1EXAMPLE 4⁽*⁾ 5⁽*⁾ 6⁽*⁾ 7 8 9 1^(st) Step S-SBR 90 90 90 90 90 90 BR 3535 35 35 35 35 Silica 70 70 70 70 70 70 TESPT 5.6 5.6 5.6 5.6 5.6 5.6Stearic acid 2 2 2 2 2 — Aromatic oil 8 8 8 8 8 8 Microcrystalline 1 1 11 1 1 wax 2^(nd) Step Zinc oxide 2.5 2.5 2.5 2.5 2.5 2.5 Antioxidant 2 22 2 2 2 3^(rd) Step Bardac ® LF-80 — — 2.8 — — — Ammonium salt — — — 2.8— — (1) Ammonium salt — — — — 2.8 — (2) Ammonium salt 3.3 (3) DPG 1.9 —— — — — CBS 2 2 2 2 2 2 Sulphur 1.2 1.2 1.2 1.2 1.2 1.2⁽*⁾comparative.

-   S-SBR: styrene/butadiene copolymer, obtained by solution    polymerization, containing 25% by weight of styrene, mixed with 37.5    phr of oil (Buna® 5025—Bayer);-   BR: cis-1,4-polybutadiene (Europrene® BR 40—EniChem Elastomeri);-   Silica: precipitated silica (Zeosil® 1165 MP—Rhone-Poulenc);-   TESPT: bis(3-triethoxysilylpropyl)tetrasulfide (X50S comprising 50%    of carbon black and 50% of silane—Degussa-Hüls—the reported amount    relates to the silane amount);-   Bardac® LF-80: dioctyl dimethyl ammonium chloride, 80% active form    (Lonza);-   Ammonium salt (1): ammonium salt of Example 1;-   Ammonium salt (2): ammonium salt of Example 2;-   Ammonium salt (3): ammonium salt of Example 3;-   Antioxidant: N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine; DPG    (secondary accelerator): N-N′-diphenylguanidine; CBS (primary    accelerator): N-cyclohexyl-2-benzotiazyl-sulfenamide (Vulkacit®    CZ—Bayer);

The Mooney viscosity ML(1+4) at 100° C. was measured, according to ISOstandard 289/1, on the non-crosslinked compositions obtained asdescribed above. The results obtained are given in Table 2.

Said elastomeric compositions were also submitted to a MDR rheometricanalysis using a MDR rheometer from Monsanto, the tests being run at170° C. for 20 minutes, with an oscillation frequency of 1.66 Hz (100oscillations per minute) and an oscillation amplitude of ±0.50. Thestatic mechanical properties according to ISO standard 37 as well ashardness in IRHD degrees at 23° C. according to ISO standard 48 weremeasured on samples of said elastomeric compositions cross-linked at170° C. for 10 minutes. The results obtained are given in Table 2.

Also given in Table 2 are the dynamic mechanical properties measuredusing an Instron dynamic device in the traction-compression modeaccording to the following methods. A test piece of the crosslinkedmaterial having a cylindrical form (length=25 mm; diameter=14 mm)compression-preloaded up to 25% longitudinal deformation with respect tothe initial length and kept at the prefixed temperature (23° C. and 70°C.) for the whole duration of the test, was submitted to a dynamicsinusoidal strain with an amplitude ±3.33% with respect to the lengthunder pre-load, with a frequency of 100 Hz. The dynamic mechanicalproperties are expressed in terms of dynamic elastic modulus (E′) andtandelta (loss factor) values. As is known, the tandelta value iscalculated as a ratio between the viscous modulus (E″) and the elasticmodulus (E′), both of them being determined with the above dynamicmeasurements.

Lastly the DIN abrasion values were measured according to DIN standard53516, also reported in Table 2, expressed as the amount of compoundremoved. TABLE 2 EXAMPLE 4⁽*⁾ 5⁽*⁾ 6⁽*⁾ 7 8 9 Mooney 74.20 87.20 65.4076.70 76.60 77.9 viscosity ML (1 + 4) STATIC MECHANICAL PROPERTIESStress at 14.11 16.24 13.41 14.97 13.91 11.70 break (MPa) Elongation426.00 612.10 406.90 440.50 374.30 374.0 at break (MPa) DYNAMICMECHANICAL PROPERTIES E′ (23° C.) 8.277 7.735 6.974 7.791 7.784 7.080 E′(70° C.) 5.988 5.446 5.510 5.940 5.953 5.241 Tandelta 0.268 0.282 0.2240.233 0.226 0.236 (23° C.) Tandelta 0.140 0.165 0.110 0.122 0.120 0.134(70° C.) RHEOMETRIC PROPERTIES ML (dN M) 3.08 4.03 2.20 2.75 3.09 3.14MH (dN m) 20.51 22.07 17.89 19.05 18.99 21.19 t30 (min) 2.13 2.40 2.161.52 1.06 1.17 t90 (min) 4.12 13.18 5.63 5.64 3.69 5.19 IRHD 69.7 66.965.3 67.1 68.8 70.0 Hardness (23° C.) IRHD 64.7 60.8 62.1 62.7 63.6 64.2Hardness (100° C.) DIN 86.3 74.3 100.7 85.1 84.4 76.0 Abrasion⁽*⁾comparative.

The results given in Table 2 show that the crosslinkable compositioncomprising the organic quaternary ammonium salt according to the presentinvention (Examples 7, 8 and 9) has high vulcanization rate withoutimpairing mechanical properties (both static and dynamic). Moreover,with respect to the elastomeric composition including different organicquaternary ammonium salt (Example. 6), an improved abrasion resistanceis achieved.

1-50. (canceled)
 51. A tyre for a vehicle wheel, comprising at least onestructural element comprising an elastomeric composition, theelastomeric composition comprising: at least one diene elastomericpolymer; and at least one organic quaternary ammonium salt having afollowing general formula (I):

wherein R represents a linear or branched C₁-C₂₂ alkylene group; alinear or branched C₂-C₂₂ alkenylene group; a C₆-C₁₈ arylene group;and/or a C₇-C₂₀ alkylarylene or alkylenearylene group; the group orgroups optionally containing at least one heteroatom selected fromoxygen, nitrogen, and/or sulfur, wherein R₁ and R₂, which may beidentical or different, represent a linear or branched C₁-C₂₂ alkylgroup; a linear or branched C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group;and/or a C₇-C₂₀ arylalkyl or alkylaryl group; the group or groupsoptionally containing at least one heteroatom selected from oxygen,nitrogen, and/or sulfur; or, R₁ and R₂, considered jointly with thenitrogen atom to which they are linked, represent a C₅-C₁₈ heterocyclicring optionally containing a second heteroatom selected from oxygen,nitrogen, and/or sulfur; or, R₁ and R₅ and/or R₂ and R₃, consideredjointly with the nitrogen atoms to which they are linked, represent aC₅-C₁₈ heterocyclic ring, wherein R₃, R₄, and R₅, which may be identicalor different, represent a linear or branched C₁-C₂₂ alkyl group; alinear or branched C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group; a C₇-C₂₀arylalkyl or alkylaryl group; and/or a group having a following formula:

wherein R, R₁, and R₂, have the same meanings as disclosed above; or twofrom R₃, R₄, and R₅, considered jointly with the nitrogen atom to whichthey are linked, represent a C₅-C₁₈ heterocyclic ring optionallycontaining a second heteroatom selected from oxygen, nitrogen, and/orsulfur, wherein X^(n−) represents an inorganic or organic anion group,and wherein n represents 1, 2, or
 3. 52. The tyre of claim 51,comprising: a carcass structure; a belt structure; a tread band; and apair of sidewalls; wherein the carcass structure comprises at least onecarcass ply, wherein the at least one carcass ply is shaped in asubstantially toroidal configuration, wherein opposite lateral edges ofthe carcass structure are associated with respective bead wires, whereineach bead wire is enclosed in a respective bead, wherein the beltstructure comprises at least one belt strip applied in acircumferentially external position relative to the carcass structure;wherein the tread band is superimposed circumferentially on the beltstructure, wherein the sidewalls are applied laterally on opposite sidesrelative to the carcass structure, and wherein the at least onestructural element comprising the elastomeric composition is the treadband.
 53. The tyre of claim 51, wherein the elastomeric composition issubstantially free of additional secondary accelerators.
 54. The tyre ofclaim 51, wherein the elastomeric composition is substantially free ofdiphenyl guanidine (DPG).
 55. The tyre of claim 51, wherein X^(n−) isselected from: halide ions such as iodine, bromine, fluorine, orchlorine ions; ipoiodite ion; ipobromite ion; fluorite ion; chloriteion; iodite ion; bromite ion; fluorine ion; chlorite ion; iodate ion;bromate ion; fluorate ion; chlorate ion; periodate ion; perbromate ion;perfluorate ion; perchlorate ion; nitrate ion; nitrite ion; sulfate ion;sulfite ion; phosphate ion; phosphite ion; hydroxide ion; or an aniongroup represented by a following formulae (II) to (V):RCOO⁻   (II) wherein R₆ represents a linear or branched C₁-C₁₈ alkylgroup; a linear or branched C₂-C₁₈ alkenyl group; a C₆-C₁₈ aryl group;or a C₇-C₂₀ arylalkyl or alkylaryl group; the group or groups optionallycontaining at least one of the following: a hydroxyl group, a carbonylgroup, an ether group, a thioether group, and/or an ester group;⁻OCO—(R₇)_(m)—COO⁻   (III) wherein m represents 0 or 1; R₇ represents alinear or branched C₁-C₁₈ alkylene group; a linear, branched or cyclicC₂-C₁₈ alkenylene group; a C₆-C₁₈ arylene group; or a C₇-C₂₀arylalkylene or alkylarylene group; the group or groups optionallycontaining at least one of the following: a hydroxyl group, a carbonylgroup, an ether group, a thioether group, and/or an ester group;R₈SO_(p) ⁻   (IV) wherein p represent 3 or 4; R₈ represents a linear orbranched C₁-C₁₈ alkyl group; a linear or branched C₂-C₁₈ alkenyl group;a C₆-C₁₈ aryl group; or a C₇-C₂₀ arylalkyl or alkylaryl group; the groupor groups optionally containing at least one of the following: ahydroxyl group, a carbonyl group, an ether group, a thioether group,and/or an ester group;

wherein p represents 3 or 4; R₉ and R₁₀, which may be identical ordifferent, represent a hydrogen atom; a linear or branched C₁-C₁₈ alkylgroup; a linear or branched C₂-C₁₈ alkenyl group; a C₆-C₁₈ aryl group;and/or a C₇-C₂₀ arylalkyl or alkylaryl group; the group or groupsoptionally containing at least one of the following: a hydroxyl group, acarbonyl group, an ether group, a thioether group, and/or an estergroup.
 56. The tyre of claim 55, wherein R and R₇ represent one or moreof: methylene, ethylene, propylene, butylene,2,2-dimethyl-1,3-propylene, hexylene, 2-methyl-3-ethyl-1,4-butylene,octylene, vinylene, butenylene, isobutenylene, pentenylene, hexenylene,phenylene, naphtylene, diphenylene, benzenylene, phenylmethylene,phenylethylene, naphtylmethylene, naphtylethylene, methylphenylene,ethylphenylene, methylnaphthylene, and ethylnaphthylene.
 57. The tyre ofclaim 55, wherein R₁, R₂, R₃, R₄, R₅, R₆, R₈, R₉, and R₁₀ represent oneor more of: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl,hexyl, octyl, allyl, methallyl, 2-butenyl, propenyl, hexenyl, octenyl,benzyl, phenyl, naphthyl, methylbenzyl, ethylbenzyl, diphenyl,methylphenyl, ethylphenyl, methylnaphthyl, and ethylnaphthyl.
 58. Thetyre of claim 51, wherein R₁ and R₂, considered jointly with thenitrogen atom or atoms to which they are linked, represent one or moreof: morpholine, pyrrolidine, piperidine, N-methyl-piperidine,piperazine, thiomorpholine, thiazolidine, benzothiazolidine, andimidazole.
 59. The tyre of claim 51, wherein R₁ and R₅ and/or R₂ and R₃,considered jointly with the nitrogen atoms to which they are linked,represent one or more of: piperazine and 1,8-diazabicyclo[2.2.2]octane.60. The tyre of claim 51, wherein in a case wherein two from R₃, R₄, andR₅, considered jointly with the nitrogen atom or atoms to which they arelinked, represent a C₅-C₁₈ heterocyclic ring, the heterocyclic ring orrings represent one or more of: pyrrolidinium, piperidinium,piperazinium, and imidazolium.
 61. The tyre of claim 51, wherein the atleast one organic quaternary ammonium salt is present in the elastomericcomposition in an amount from 0.1 phr to 10 phr.
 62. The tyre of claim51, wherein the at least one organic quaternary ammonium salt is presentin the elastomeric composition in an amount from 0.5 phr to 5 phr. 63.The tyre of claim 51, wherein the at least one diene elastomeric polymerhas a glass transition temperature (T_(g)) below 20° C.
 64. The tyre ofclaim 63, wherein the at least one diene elastomeric polymer comprisesone or more of: cis-1,4-polyisoprene; 3,4-polyisoprene; polybutadiene;optionally halogenated isoprene/isobutene copolymers;1,3-butadiene/acrylonitrile copolymers; styrene/1,3-butadienecopolymers; styrene/isoprene/1,3-butadiene copolymers; andstyrene/1,3-butadiene/acrylonitrile copolymers.
 65. The tyre of claim51, wherein the elastomeric composition further comprises at least oneelastomeric polymer of one or more monoolefins with an olefiniccomonomer or derivatives thereof.
 66. The tyre of claim 65, wherein theat least one elastomeric polymer comprises one or more of:ethylene/propylene copolymers (EPR) or ethylene/propylene/dienecopolymers (EPDM); polyisobutene; butyl rubbers; and halobutyl rubbers.67. The tyre of claim 51, wherein the elastomeric composition furthercomprises at least one primary accelerator.
 68. The tyre of claim 67,wherein the at least one primary accelerator is selected from thiazoles,sulphenamides, and/or xanthogenates.
 69. The tyre of claim 67, whereinthe at least one primary accelerator is selected from sulphenamides. 70.The tyre of claim 67, wherein the at least one primary accelerator ispresent in the elastomeric composition in an amount from 0.1 phr to 10phr.
 71. The tyre of claim 67, wherein the at least one primaryaccelerator is present in the elastomeric composition in an amount from0.5 phr to 5 phr.
 72. The tyre of claim 51, wherein the elastomericcomposition further comprises at least one reinforcing filler in anamount between 0.1 phr and 120 phr.
 73. The tyre of claim 72, whereinthe at least one reinforcing filler comprises carbon black.
 74. The tyreof claim 72, wherein the at least one reinforcing filler comprisessilica.
 75. The tyre of claim 74, wherein the elastomeric compositionfurther comprises a silica coupling agent.
 76. A tread band for a tyre,the tread band comprising a crosslinkable elastomeric composition, theelastomeric composition comprising: at least one diene elastomericpolymer; and at least one organic quaternary ammonium salt having afollowing general formula (I):

wherein R represents a linear or branched C₁-C₂₂ alkylene group; alinear or branched C₂-C₂₂ alkenylene group; a C₆-C₁₈ arylene group;and/or a C₇-C₂₀ alkylarylene or alkylenearylene group; the group orgroups optionally containing at least one heteroatom selected fromoxygen, nitrogen, and/or sulfur, wherein R₁ and R₂, which may beidentical or different, represent a linear or branched C₁-C₂₂ alkylgroup; a linear or branched C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group;and/or a C₇-C₂₀ arylalkyl or alkylaryl group; the group or groupsoptionally containing at least one heteroatom selected from oxygen,nitrogen, and/or sulfur; or, R₁ and R₂, considered jointly with thenitrogen atom to which they are linked, represent a C₅-C₁₈ heterocyclicring optionally containing a second heteroatom selected from oxygen,nitrogen, and/or sulfur; or, R₁ and R₅ and/or R₂ and R₃, consideredjointly with the nitrogen atoms to which they are linked, represent aC₅-C₁₈ heterocyclic ring, wherein R₃, R₄, and R₅, which may be identicalor different, represent a linear or branched C₁-C₂₂ alkyl group; alinear or branched C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group; a C₇-C₂₀arylalkyl or alkylaryl group; and/or a group having a following formula:

wherein R, R₁, and R₂, have the same meanings as disclosed above; or twofrom R₃, R₄, and R₅, considered jointly with the nitrogen atom to whichthey are linked, represent a C₅-C₁₈ heterocyclic ring optionallycontaining a second heteroatom selected from oxygen, nitrogen, and/orsulfur, wherein X^(n−) represents an inorganic or organic anion group,and wherein n represents 1, 2, or
 3. 77. The tread band of claim 76,wherein the elastomeric composition is substantially free of additionalsecondary accelerators.
 78. The tread band of claim 76, wherein theelastomeric composition is substantially free of diphenyl guanidine(DPG).
 79. The tread band of claim 76, wherein the at least one organicquaternary ammonium salt is present in the elastomeric composition in anamount from 0.1 phr to 10 phr.
 80. The tread band of claim 76, whereinthe at least one diene elastomeric polymer has a glass transitiontemperature (T_(g)) below 20° C.
 81. The tread band of claim 76, whereinthe elastomeric composition further comprises at least one elastomericpolymer of one or more monoolefins with an olefinic comonomer orderivatives thereof.
 82. The tread band of claim 76, wherein theelastomeric composition further comprises at least one primaryaccelerator.
 83. The tread band of claim 82, wherein the at least oneprimary accelerator is selected from thiazoles, sulphenamides, and/orxanthogenates.
 84. The tread band of claim 76, wherein the elastomericcomposition further comprises at least one reinforcing filler in anamount between 0.1 phr and 120 phr.
 85. The tread band of claim 84,wherein the at least one reinforcing filler comprises carbon black. 86.The tread band of claim 84, wherein the at least one reinforcing fillercomprises silica.
 87. The tread band of claim 86, wherein theelastomeric composition further comprises a silica coupling agent.
 88. Acrosslinkable elastomeric composition, comprising: at least one dieneelastomeric polymer; and at least one organic quaternary ammonium salthaving a following general formula (I):

wherein R represents a linear or branched C₁-C₂₂ alkylene group; alinear or branched C₂-C₂₂ alkenylene group; a C₆-C₁₈ arylene group;and/or a C₇-C₂₀ alkylarylene or alkylenearylene group; the group orgroups optionally containing at least one heteroatom selected fromoxygen, nitrogen, and/or sulfur, wherein R₁ and R₂, which may beidentical or different, represent a linear or branched C₁-C₂₂ alkylgroup; a linear or branched C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group;and/or a C₇-C₂₀ arylalkyl or alkylaryl group; the group or groupsoptionally containing at least one heteroatom selected from oxygen,nitrogen, and/or sulfur; or, R₁ and R₂, considered jointly with thenitrogen atom to which they are linked, represent a C₅-C₁₈ heterocyclicring optionally containing a second heteroatom selected from oxygen,nitrogen, and/or sulfur; or, R₁ and R₅ and/or R₂ and R₃, consideredjointly with the nitrogen atoms to which they are linked, represent aC₅-C₁₈ heterocyclic ring, wherein R₃, R₄, and R₅, which may be identicalor different, represent a linear or branched C₁-C₂₂ alkyl group; alinear or branched C₂-C₂₂ alkenyl group; a C₆-C₁₈ aryl group; a C₇-C₂₀arylalkyl or alkylaryl group; and/or a group having a following formula:

wherein R, R₁, and R₂, have the same meanings as disclosed above; or twofrom R₃, R₄, and R₅, considered jointly with the nitrogen atom to whichthey are linked, represent a C₅-C₁₈ heterocyclic ring optionallycontaining a second heteroatom selected from oxygen, nitrogen, and/orsulfur, wherein X^(n−) represents an inorganic or organic anion group,and wherein n represents 1, 2, or
 3. 89. The elastomeric composition ofclaim 88, wherein the elastomeric composition is substantially free ofadditional secondary accelerators.
 90. The elastomeric composition ofclaim 88, wherein the elastomeric composition is substantially free ofdiphenyl guanidine (DPG).
 91. The elastomeric composition of claim 88,wherein the at least one organic quaternary ammonium salt is present inthe elastomeric composition in an amount from 0.1 phr to 10 phr.
 92. Theelastomeric composition of claim 88, wherein the at least one dieneelastomeric polymer has a glass transition temperature (T_(g)) below 20°C.
 93. The elastomeric composition of claim 88, further comprising atleast one elastomeric polymer of one or more monoolefins with anolefinic comonomer or derivatives thereof.
 94. The elastomericcomposition of claim 88, further comprising at least one primaryaccelerator.
 95. The elastomeric composition of claim 94, wherein the atleast one primary accelerator is selected from thiazoles, sulphenamides,and/or xanthogenates.
 96. The elastomeric composition of claim 88,further comprising at least one reinforcing filler in an amount between0.1 phr and 120 phr.
 97. The elastomeric composition of claim 96,wherein the at least one reinforcing filler comprises carbon black. 98.The elastomeric composition of claim 96, wherein the at least onereinforcing filler comprises silica.
 99. The elastomeric composition ofclaim 98, wherein the elastomeric composition further comprises a silicacoupling agent.
 100. A crosslinked elastomeric manufactured productobtained by crosslinking the elastomeric composition of claim 88.